Using find / will normally be very slow. Using locate is much faster but somewhat imprecise because it doesn't support anything more complex than substring matching. A directory called .pembroke will be found and returned by locate along with every file inside it.

A combination of locate and grep, however, has speed and precision. Conveniently, it also does not require sudo.

locate .pem | grep "\.pem$"

The downside? The database locate uses is normally only updated once per day so any recent changes (additions, deletions, name changes, etc.) will not be found.